The present invention relates to a method of monitoring the operation of a vehicle, for example a motor vehicle, using an onboard diagnostic system of at least one electronic computer among the electronic computers for monitoring the operation of the vehicle.
A motor vehicle conventionally comprises a plurality of onboard electronic computers, when appropriate connected to sensors and actuators, to perform various vehicle operation monitoring functions, such as monitoring the engine injection system, monitoring an automatic gearbox, managing vehicle links to the ground (braking, suspension, etc.), and so on.
To ensure the safety of the users faced with a possible operating fault detected on a component or a system relating to the operation of a vehicle and to allow for it to be repaired by a garage mechanic, the onboard computers of the self-diagnostic systems make it possible to implement various electrical or functional diagnostic strategies.
These diagnostic strategies can be applied permanently (as is the case, for example, with electrical continuity diagnostics) or in specific operating conditions (as is the case with functional diagnostics, for example diagnostics of the supercharging system or of the catalytic conversion efficiency of the exhaust gas post-treatment system).
The function of these diagnostic strategies is to provide the computer with failure information, with which is associated a status (for example “present”, “absent”).
The computer then uses this failure information and the associated status information to apply strategies of reconfiguration (use, for example, of a replacement value when a sensor fails) and/or of degraded mode operation (for example, limitation of the engine performance if a failure of the supercharging system is detected).
These strategies aim, in strictly descending order, to guarantee the safety of the users and of the environment, to ensure the reliability of the hardware and to minimize the impact felt by the user.
Most of the current onboard diagnostic systems consider four possible states for the failures, briefly described below:                “failure absent”: this status indicates that, for the last result supplied by the onboard diagnostic strategy on the current operating cycle, there is no failure. Typically, when the system is initialized at the start of a new vehicle usage cycle, the status of all the possible failures take this value.        “failure present”: this status indicates that, for the last diagnostic result supplied by the onboard diagnostic strategy on the current operating cycle, there is a failure. This failure state is not designed to be stored on the loss of power supply at the end of a vehicle usage cycle.        “failure stored”: this status indicates that since the last time the fault memory of the computer concerned was erased by an external diagnostic tool, the failure has been detected at least once. This status does not relate to the current operating cycle and can therefore be added to the two previous states. Thus, a failure can be absent and stored, or present and stored. This stored failure state is in fact intended for logging purposes.        “OBD confirmed failure”: this status relates to the failures of the OBD scope, in other words the “onboard diagnostic” (OBD) type system, compliant with the ISO 14 230-4 standard, intended to monitor the emissions of pollutants, by detecting the probable origin of a malfunction, that is, a failure of a component or of a system relating to the emissions, which results in the emission limits set down according to international standards being exceeded. The onboard diagnostic system OBD can therefore relate to several computers of one and the same motor vehicle, possibly having an influence on the emissions of pollutants, such as the engine monitoring computer or that of the automatic gearbox.        
According to the ISO 14229-UDS (Unified Diagnostic Services) standard, the definitions of the above states are complemented by the following states:                “failure present on operating cycle”: this status is identical to the “failure present” status, but is maintained until the end of the operating cycle.        “OBD failure present on the running cycle and/or on the preceding one”: this status corresponds to a failure undergoing OBD confirmation.        
The abovementioned standard also generalizes to all failures the concept of “readiness”, previously used for the failures of the OBD scope, to indicate, in the form of binary information, whether the diagnostic strategy concerned has been performed or not, based on two levels of information: on the operating cycle and since the last time the fault memory of the computer was erased by an external diagnostic tool.
The duly defined information provides, on the one hand, effective help in repairing any failures and, on the other hand, makes it possible to manage most of the reconfigurations and/or degraded modes needed in the event of failure.
However, the failure states supplying the diagnostic results for the failures concerned, as used for most of the motor vehicle operation monitoring systems, do not always allow for total observance of the above-mentioned objectives, namely guaranteeing the safety of users and the environment, guaranteeing the reliability of the hardware and minimizing the impact on the environment.
In particular, when a new vehicle usage cycle is started, the onboard diagnostic system of each computer initializes all the abovementioned failure states, apart from the stored failures. More specifically, a computer assumes, at the start of each new vehicle usage cycle, that all of the onboard diagnostic system is in the nominal state. Also, the information relating to the last diagnostic performed before the loss of power supply cannot be recovered for the next usage cycle.
At the start of a new cycle, the system cannot therefore apply any reconfiguration or any degraded operating mode, even if a failure is physically present on the vehicle. This situation will remain true as long as the first diagnostic phase proper is not executed and the failure concerned is not redetected by the system.
Consequently, if a physical failure remains, the onboard diagnostic system, from its initialization to the new detection of this failure, will operate in a “pseudo-nominal” state, that is, without any reconfiguration and/or degraded mode strategy being applied, which can induce risks of additional degradations, even safety risks for the users and/or the environment.
As an example, the detection of a fuel leak requires, for reasons of reliability of the diagnostic strategy, the system to operate for a minimum time (detection time) in a given operating mode (detection zone). The diagnostic can therefore be applied only after several minutes of operation and/or kilometers traveled. Thus, when a leak has been detected during a vehicle usage cycle, it would be desirable, from the start of the next running cycle, to be able to inform the driver thereof by an appropriate means (lighting of an indicator, for example) without, for this, it being necessary to wait for the diagnostic strategy to be executed for this new usage cycle, all the more so as the vehicle can have multiple users, who do not necessarily know the history of the previous running cycles.
The use of the “failure stored” state is also not suited to the effect of reproducing the last diagnostic result for a failure concerned at the start of a subsequent usage cycle. Indeed, this state for a failure concerned is irreversible and therefore requires the vehicle to be returned to a garage for erasure. Now, the fact that many failures can self-repair (for example a temporary mechanical blockage of a component) or possibly be repaired by the user himself (for example reconnection of a sensor) must be taken into account. Since the “failure stored” state is generally irreversible from one cycle to another, it could not therefore allow the system to return to the nominal mode if the failure concerned was no longer detected.